Crop defaults to true, added behaviour to crop = false

For now, the crop parameter was unused.
It is now set to true by default.
If you pass crop: false to the parameters, il will resize, but without cropping.

**Exemple with a 1200px x 800px source image**
![image](https://cloud.githubusercontent.com/assets/3499603/5106698/29f008d2-6ffb-11e4-9b11-64fcb5c869ad.png)

```php
bfi_thumb("URL-to-image.jpg", array(
    'width' => 100,
    'height' => 100
));
```
This code will result, as expected, in a 100 x 100 pixels image.
![image](https://cloud.githubusercontent.com/assets/3499603/5106710/3ded2252-6ffb-11e4-879d-52bc9d3b86bf.png)

Yet, if you use this syntax :
```php
bfi_thumb("URL-to-image.jpg", array(
    'width' => 100,
    'height' => 100,
   'crop' => false
));
```

It will result in an image that is 100 x 67 pixels, and not cropped.
![image](https://cloud.githubusercontent.com/assets/3499603/5106717/554c0166-6ffb-11e4-8d2a-7f3a04c5a6bc.png)

Of course, you can still grow images.
And by the way, I used an autoformat tool... Hope you don't mind ;)